As long as all of the image is processed by the GPU, it's self consistent. The OpenCL processing has a 2 pixel offset in both X & Y. I think that this is the essence of the problem. Only the "Minimum" setting generates artifacts that appear as rectangular areas that "Do Not Shift by 2 pixels". And of course NONE if OpenCL is disabled.Ĭomparing the output of the 4 settings to NONE as the reference standard shows:Īll 4 OpenCL settings shift the output image by 2 pixels in both X & Y. There are 4 OpenCL utilization settings: Minimum, Low, Standard, High. I've identified the specifics of the problem! My immediate question is regarding Aftershot Pro 3 on Linux, but I'm now curious as to a more extensive "Difference" check across many platforms and RAW editors that support using GPUs. The most obvious one is a perfectly horizontal thin line through the cat's forehead. The CPU only, GPU OpenCL, Difference images can be seen at:īouncing back and forth between the two main images allows you to see the artifact shift points. I'm running the latest Nvidia drivers on an arguably old GPU, but that should only be a speed issue. Has anyone else encountered this problem? I tried the samething in Darktable and got exactly what one would hope to get, a black "Difference" as the images were identical.ĪfterShot has small brightness differences with OpenCL hardware acceleration that's small enough to live with, but the block artifacts are unacceptable. The artifacts turned out to be more extensive than I initially saw and manifest as several rectangular block discontinuities. I put both "with" and "without" OpenCL JPGs in GIMP layers and did a "Difference" of the two layers. I'm running Linux and have not tried this on Windows. Exporting with OpenCl disabled did not generate the artifact. Initially I thought, "Oh no, I have a camera problem!" Further experimenting demonstrated that the artifacts are generated when exporting raw to JPG with OpenCL enabled to use my Nvidia GPU. I discovered an artifact on a shot when I printed a large blowup of a tight crop.
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